In recent years, with the spread of personal digital assistants and the spread of living style in which individuals personally enjoy video and music, demands for inner-ear headphones with high sound quality are increasing. The shape of an auditory pore into which an inner-ear headphone is inserted greatly varies among users. Therefore, in order to improve wearing sensations of many users, a small-size loudspeaker with a high degree of freedom in case design is demanded. In addition, as for a loudspeaker used in a receiver of a hearing aid, a small-size loudspeaker is demanded which has a wide frequency band for sound output, and causes a user to feel less discomfort or unpleasantness when it is inserted in his/her auditory pore.
As an example of a loudspeaker used for an inner-ear headphone or a hearing aid, a balanced armature type loudspeaker which is a kind of a magnetic loudspeaker is widely used. Although the balanced armature type loudspeaker can be reduced in size, since the displacement amplitude of an armature that drives a diaphragm is small because of the structure of the loudspeaker, it is difficult to reproduce a low-pitched sound which needs a large amplitude.
As a prior art literature relating to the present disclosure, Patent Literature 1 has been known, for example. Patent Literature 1 discloses a small-size electrodynamic loudspeaker capable of reproduction of low-pitched sound. In the loudspeaker, a support member that supports a diaphragm in a vibratable manner is composed of a plurality of edges, and a magnetic fluid fills a space between a voice coil and a plate, in a magnetic gap.